1. Field of the Invention
The present invention relates generally to methods for fabricating thin film magnetic heads, and more particularly to the use of anti-reflective coatings in photolithographic process steps for fabricating narrow components such as pole tips of magnetic heads.
2. Description of the Prior Art
The magnetic pole pieces of thin film magnetic heads are generally fabricated utilizing photolithographic techniques that are well known to those skilled in the art. The ongoing efforts to increase the areal data storage density on magnetic media has led to a need to fabricate magnetic pole pieces with a smaller width, because the width of the pole pieces, particularly the P2 pole tip width, generally determines the track width of the data track written by the magnetic head. A problem that occurs in the use of photolithographic techniques in fabricating components with such small dimensions is the unwanted reflection of the exposing light energy from the surface of the substrate upon which the photolithographic resist is formed. The reflected light can expose the photoresist in unintended areas, thus degrading the accuracy of the photolithographic process. The present invention solves this problem through the use of a bottom antireflection coating (BARC) in the photolithographic process.
The use of BARC coating in the semiconductor process industry for making integrated circuits and the like is well known. However the use of such BARC coatings in the magnetic head fabrication industry, as well as the particular BARC coating process parameters described herein has not heretofore been accomplished.
The fabrication method of the present invention involves the utilization of a bottom antireflective coating (BARC) to eliminate the deleterious effects of unwanted reflected light during the photo exposure step of a photolithographic process. The BARC coating is particularly effective where small components, such as a pole tip of a magnetic head, are photolithographically fabricated. The BARC coating of the present invention is comprised of a carbon coating having a thickness of approximately 300 angstroms, and to obtain good adherence of the carbon coating to a substrate layer, an initial coating layer of silicon is deposited before the carbon coating. The silicon coating layer is formed with a thickness of approximately 20 angstroms. A carbon ion beam deposition tool is preferably utilized to deposit the carbon layer. Where the BARC layer is utilized in a photolithographic process to fabricate a NiFe pole tip, a NiFe seed layer is first deposited upon a substrate, such as the write gap layer of a magnetic head. An adhesion layer may be deposited prior to the NiFe seed layer if necessary. The BARC layer of the present invention is then formed on the NiFe seed layer and the pole tip trench is then photolithographically created. The BARC layer eliminates reflected light during the photoexposure step, resulting in more faithfully reproduced trench walls. Thereafter, the BARC layer is removed from the bottom of the trench, utilizing a reactive ion etch process, such that the surface of the NiFe seed layer is exposed. The NiFe pole tip is then fabricated into the trench, and thereafter the remaining photoresist and the remaining BARC layer are removed. The use of the BARC layer therefore is not apparent in the finally fabricated magnetic head; however, the dimensional characteristics of the pole tip are improved.
It is an advantage of the fabrication method of the present invention that increased accuracy is obtained in the photolithographic fabrication of small components of magnetic heads.
It is another advantage of the fabrication method of the present invention that a carbon BARC antireflective coating has been developed for use in the photolithographic fabrication of magnetic head components.
It is a further advantage of the fabrication method of the present invention that it utilizes a BARC coating comprised of carbon.
It is yet another advantage of the fabrication method of the present invention that it utilizes carbon and carbon deposition tools that are generally already utilized in the fabrication of magnetic heads, such that new fabrication tools and chemistries are not introduced into the magnetic head manufacturing process.
These and other features and advantages of the present invention will no doubt become well understood by those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawings.